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MicroRNAs (miRNAs) are non-coding RNAs that regulate gene expression at the posttranscriptional level. In this study, the function of microRNA-7 (miR-7) in host-virus interaction was investigated. Replication of White spot syndrome virus (WSSV) was enhanced with the overexpression of miR-7 and inhibited with the downregulation of miR-7 by using anti-miRNA oligonucleotide AMO-miR-7. The target gene of miR-7 was predicted using bioinformatics methods. Results showed that crab myeloid differentiation factor 88 (Myd88) could be targeted by miR-7. When the expression of Myd88 was knocked down by sequence-specific siRNA, WSSV copies in crabs were significantly increased. Further findings revealed that knockdown of Myd88, Tube, or Pelle inhibited the expressions of interleukin enhancer-binding factor 2 homolog (ILF2) and interleukin-16-like gene (IL-16L). While ILF2 was silenced, IL-16L expression was inhibited. The overexpression of miR-7 inhibited the expressions of ILF2 and IL-16L. Moreover, when ILF2 or IL-16L was silenced, WSSV copies in crabs were increased. Thus, the upregulated expression of miR-7 during WSSV challenge suppressed the host Myd88-ILF2-(IL-16L) signaling pathway in crabs and enhanced WSSV replication. Our study indicated that WSSV utilized crab miR-7 to enhance virus replication during infection.WSSV utilized crab miR-7 to enhance virus replication during infection.The target gene of miR-7 was crab myeloid differentiation factor 88 (Myd88).MiR-7 targeting Myd88 inhibited the host Myd88-ILF2-(IL-16L) signaling pathway.Myd88-ILF2-(IL-16L) pathway had a negative effect on virus replication.